Assessing Long-range Forecasts

Weatherwords

January 22, 2001|By Dr. Mel Goldstein

Long-range forecasting can come up quite short.

Here's a long-range forecast from the ``Farmer's Almanac'' for this winter season: ``The winter of 2000-01 should get off to a late start and turn out to be milder than average, even less severe than last year.''

I guess some things just don't work out. Still, that publication's competitor, the original ``Old Farmer's Almanac,'' seemed closer to the mark: ``November and December will be colder than normal before a substantial January thaw.''

This is the week that the thaw typically takes place, and our weather will be moderating, but that substantial January thaw hasn't yet surfaced. The National Weather Service predicted a colder-than-normal season with precipitation near or somewhat above normal -- a season closer to a normal winter than the seasons we've grown to know in recent years. So maybe those long-range seasonal forecasts aren't all off base. In New England, November and December were much colder than normal, and across the country the weather was record cold. And now in January, even though snow has yet to melt from the landscape, the arctic cold has certainly vanished.

One of the most impressive advances in weather forecasting relates to the understanding of the interaction between the ocean and the atmosphere. The atmosphere drives the ocean, but the ocean can also drive the atmosphere. Cyclical changes in ocean temperature, such as El Nino and La Nina, will influence flow patterns above the sea. Those patterns will prevail for a season, sometimes a year. The oceans are providing a new wave of understanding to the weather.